waypoint_compass/init.lua

local player_waypoints = {}
local update_interval = 1.31415
local compass_precision = 10 -- set to 1 to show whole number or 10 for 1 decimal
local waypoint_color = 0xFC7D0A
local target_above = false -- place waypoint inside the block or above it
local point_to_objects = false -- unimplemented
local point_to_liquids = true
local compass_range = 180

-- lua metatables? what is that? :P
-- local function get_compass_meta_id(meta)
--     return meta:get_string("waypoint_compass:id") ~= "" or "default_id"
-- end


local function get_compass_meta_label(meta)
    local label = meta:get_string("waypoint_compass:label")
    return label ~= "" and label or "destination"
end


local function set_compass_meta_label(meta, label)
    meta:set_string("waypoint_compass:label", label)
end


local function set_compass_meta_pos(meta, pos)
    local pos_str = minetest.serialize(pos)
    meta:set_string("waypoint_compass:position", pos_str)
end


local function get_compass_meta_pos(meta)
    return minetest.deserialize(meta:get_string("waypoint_compass:position"))
end

-- local function set_compass_meta_pos(meta, pos)
--     local pos_hash = minetest.hash_node_position(pos)
--     meta:set_int("waypoint_compass:position", pos_hash)
-- end


-- local function get_compass_meta_pos(meta)
--     return minetest.get_position_from_hash(meta:get_int("waypoint_compass:position"))
-- end

local function set_waypoint_at_pointed_place(itemstack, pointed_thing)
    if pointed_thing and pointed_thing.type == "node" then
        local pointed_pos = target_above and pointed_thing.above or pointed_thing.under
        local meta = itemstack:get_meta()
        meta:set_string("description", string.format("Waypoint compass %s", minetest.pos_to_string(pointed_pos)))
        set_compass_meta_pos(meta, pointed_pos)
        set_compass_meta_label(meta, minetest.pos_to_string(pointed_pos))
        return itemstack
    end
    -- TODO handle entities?
end


-- return first thing player is pointing at
local function raycast_crosshair(player, range)
    local p_pos = player:get_pos()
    local p_eye_height = player:get_properties().eye_height
    local p_eye_pos = { x = p_pos.x, y = p_pos.y + p_eye_height, z = p_pos.z }
    local to = vector.add(p_eye_pos, vector.multiply(player:get_look_dir(), range))
    local ray = minetest.raycast(p_eye_pos, to, point_to_objects, point_to_liquids)
    local pointed_thing = ray:next()
    return pointed_thing
    -- while pointed_thing do
    --     print(pointed_thing.type, minetest.pos_to_string(pointed_thing.under))
    --     pointed_thing = ray:next()
    -- end
end


local function hide_hud_waypoint(player)
    local player_name = player:get_player_name()
    local hud_id = player_waypoints[player_name].hud_id
    player_waypoints[player_name] = nil
    player:hud_remove(hud_id)
end


local function show_hud_waypoint(player, compass_item_meta)
    local player_name = player:get_player_name()
    -- Show this waypoint
    local waypoint_name = get_compass_meta_label(compass_item_meta)
    local hud_id = player:hud_add({
            hud_elem_type = "waypoint",
            name = waypoint_name,
            text = "m",
            precision= compass_precision,
            number = waypoint_color,
            world_pos = get_compass_meta_pos(compass_item_meta),
    })
    -- store HUD elemnt id to remove it later
    if not player_waypoints[player_name] then
        player_waypoints[player_name] = {}
    end
    --print("hud_id add", hud_id)
    player_waypoints[player_name].pos = get_compass_meta_pos(compass_item_meta)
    player_waypoints[player_name].hud_id = hud_id
end


-- if item is a compass, then show stored waypoint
local function update_hud_waypoint(player, itemstack)
    if not player:is_player() then
        return
    end
    local player_name = player:get_player_name()
    -- player is holding compass
    if (itemstack and itemstack:get_name() == "waypoint_compass:compass") then
        local meta = itemstack:get_meta()
        local waypoint_pos = get_compass_meta_pos(meta)
        -- remove different waypoint if it exists
        if player_waypoints[player_name] and
            (player_waypoints[player_name].pos ~= waypoint_pos) then
            hide_hud_waypoint(player)
        end
        -- show new waypoint
        if not player_waypoints[player_name] then
            show_hud_waypoint(player, meta)
        end
    else
        -- not holding it anymore
        if player_waypoints[player_name] then
            hide_hud_waypoint(player)
        end
    end
end


local timer = 0
minetest.register_globalstep(function(dtime)
        timer = timer + dtime
        if timer > update_interval then
            for _,player in pairs(minetest.get_connected_players()) do
                local itemstack = player:get_wielded_item()
                update_hud_waypoint(player, itemstack)
            end
            timer = 0
        end
end)


local function compass_use_callback(itemstack, user, pointed_thing)
    if pointed_thing.type == "nothing" then
        if user and user:is_player() then
            pointed_thing = raycast_crosshair(user, compass_range)
        end
    end
    set_waypoint_at_pointed_place(itemstack, pointed_thing)
    update_hud_waypoint(user, itemstack)
end

minetest.register_tool(
    "waypoint_compass:compass", {
        description = "Waypoint compass",
        short_description = "Waypoint compass",
        inventory_image = "Waypoint_compass_inventory_image.png",
        wield_scale = {x = 0.5, y = 0.5, z = 0.5},
        range = 2.0, -- TODO what's the good range?
        on_place = function(itemstack, placer, pointed_thing)
            compass_use_callback(itemstack, placer, pointed_thing)
            return itemstack
        end,
        on_secondary_use = function(itemstack, user, pointed_thing)
            compass_use_callback(itemstack, user, pointed_thing)
            return itemstack
        end,
})